1. Field of the Invention
The present invention relates to laminated coil components and manufacturing methods for laminated coil components, and particularly relates to a laminated coil component that is defined by stacking and pressure-bonding a plurality of magnetic layers where a plurality of coil conductors defining a coil are respectively included, and then calcining the pressure-bonded magnetic layers, and a manufacturing method for the laminated coil component.
2. Description of the Related Art
Examples of laminated coil components are disclosed in Japanese Patent No. 5196038 and Japanese Unexamined Patent Application Publication No. 2012-129367. According to Japanese Patent No. 5196038 and Japanese Unexamined Patent Application Publication No. 2012-129367, a coil-embedded board is made by laminating magnetic layers and nonmagnetic layers (or feebly magnetic layers). The coil is defined by applying an electrode paste on each of the magnetic layers and nonmagnetic layers in a coil shape. A material that defines an air gap is applied to a coil section so as to alleviate stress strain caused by a difference in thermal expansion coefficients between the magnetic body and the electrode material. The material that defines the air gap is provided within a contour of a circle defined by the coil in plan view of the board. The material that defines the air gap, as applied in the above-described manner, vanishes when the coil-embedding board is calcined, thus defining an air gap inside the board.
In Japanese Patent No. 5196038 and Japanese Unexamined Patent Application Publication No. 2012-129367, the coil is wound a single turn in each layer, and none of the above documents describe a structure in which the coil is wound in multiple turns in each layer so as to increase an inductance value of the coil.
If the coil includes the structure of multiple turns as described above in order to increase the inductance value, it is difficult to apply the material that defines the air gap so that it at least partially overlaps with the electrode material. In addition, since unevenness appears in each layer along a diameter direction of the coil, a sufficient pressure is not exerted in a vertical direction when the layers are stacked and pressure-bonded. This raises a risk that unintended separation occurs after the calcination.
If a micro DC-DC converter is used in a light load region, an inductance value significantly influences the conversion efficiency. A spiral structure for increasing the inductance value is considered to play an important role particularly in a laminated coil component for a micro DC-DC converter.